It is standard practice in electrical power generating and distributing systems to use bus bars which comprise a suitable electrical conductor such as copper or aluminum, and which may be up to about 8 inches wide and 1/8 inches, or a little more, thick. In such systems, it is frequently necessary to couple two or more buse bars together to provide the desired current carrying capacity and/or circuit configuration. It has been standard practice to electrically couple two or more bus bars together by means of a pair of opposing clamping plates each of which is formed by a casting process and which comprises rails, or ribs, which are joined together at large lands which extend beyond the limits of the bus bar and include bolt holes. One of these clamping plates may be placed in complementary relationship on each side of the bus bars to be electrically joined. They are coupled together, under tension, by means of fastening means such as bolts passing through the holes in the land areas to provide pressure between the bus bars and provide good electrical contact between the bus bars.
A typical prior art clamping plate provides three rails, or ribs, extending from each of the lands with the bolt hole and extending to some other land area. In a rectangular configuration, diagonal rails are also used. Clamping plates of this type have been used in the industry for an extended period of time and have served admirably under ideal conditions. However, it is not unusual to experience casting difficulties due to nonuniform solidification. That is, after the metal is poured into the mold for making the clamping plate, the relatively thin portions of the rails commence to cool and solidify earlier than the more massive land areas with the bolt hole. Since shrinkage accompanies solidification, the nonuniform solidification frequently results in minute cracks within the structure which weakens it and cause fracture thereof when the plate is applied to bus bars and the coupling bolts tightened. The cracks usually form at junctions with abrupt changes in cross-sectional areas. A fractured clamping plate can not provide adequate pressure and must be removed and replaced. The replacement problems have been reduced by means of a very careful inspection of clamping plates prior to approval for use and/or by carefully controlled temperatures and/or use of chills during solidification. This has resulted in a high rejection rate and increased manufacturing costs.